The present invention concerns an unwinding device for twin warp beams in weaving looms, providing important advantages in loom construction.
It is known that, in order to facilitate the warping operation in double-width weaving machines, it is often preferred to use, instead of a single warp beam, two side-by-side beams, called "twin beams". The unwinding of such beams is either carried out by a single unwinding device, equipped with a differential between the two beams, or by two separate unwinders.
Both solutions are meant to guarantee a constant equal tension for the two beams, so as to obtain a perfect working and to exhaust the two beams simultaneously. The tension should moreover be uniform and it should be possible to efficiently regulate the damping action of the yarn carriers and to easily operate any adjustments.
The solution of a single unwinder with a differential, because of the high transmission ratios and torques involved in the operation, is subject to intolerable slacks which determine oscillations in the beams and an anomalous behaviour. It is therefore not suited for application on modern weaving machines, with high performances and working at very fast speeds.
The solution with two separate unwinders is more interesting, as it reduces slacks and halves the torques, dividing them between the two unwinders. Furthermore, it provides the advantages of an easier installation of the beams, which are free from kinematic connections. Nevertheless, in its practical accomplishments known so far, also this solution is not suited for a rational application on modern looms with high speeds and performances.
The object of the present invention is to propose a modern and satisfactory solution for an unwinding device for twin beams.